I was thinking direct radiation, and assuming that either (1) they go deep as well as high, cooling down the magma or something, or (2) we plug them into some kind of huge mesh of highly-heat-conductive stuff all over the earth, or most likely (3) we just let the wind do its job: if some region is being cooled relative to the surrounding region, you'll get winds blowing that will equalize the temperature somewhat.

But, once again: crazy ideas.